multiprocess: align our logging with libmultiprocess's

Without this change, logging (even if unused) may account for a
substantial portion of bitcoin-node's and/or client's runtime cpu usage, due
to libmultiprocess's expensive message serialization.

This (along with some recent upstream changes) avoids the overhead by opting
out of log handling for messages that we're not interested in.

Info, Warning, and Error are logged unconditionally to match our behavior
elsewhere. See BCLog::Logger::GetCategoryLogLevel .

Author: theuni

src/ipc/capnp/protocol.cpp

@@ -30,9 +30,35 @@
 namespace ipc {
 namespace capnp {
 namespace {
+
+BCLog::Level ConvertIPCLogLevel(mp::Log level)
+{
+    switch (level) {
+        case mp::Log::Trace: return BCLog::Level::Trace;
+        case mp::Log::Debug: return BCLog::Level::Debug;
+        case mp::Log::Info: return BCLog::Level::Info;
+        case mp::Log::Warning: return BCLog::Level::Warning;
+        case mp::Log::Error: return BCLog::Level::Error;
+        case mp::Log::Raise: return BCLog::Level::Error;
+    } // no default case, so the compiler can warn about missing cases
+
+    // Be conservative and assume that if MP ever adds a new log level, it
+    // should only be shown at our most verbose level.
+    return BCLog::Level::Trace;
+}
+
+mp::Log GetRequestedIPCLogLevel()
+{
+    if (LogAcceptCategory(BCLog::IPC, BCLog::Level::Trace)) return mp::Log::Trace;
+    if (LogAcceptCategory(BCLog::IPC, BCLog::Level::Debug)) return mp::Log::Debug;
+
+    // Info, Warning, and Error are logged unconditionally
+    return mp::Log::Info;
+}
+
 void IpcLogFn(mp::LogMessage message)
 {
-    LogDebug(BCLog::IPC, "%s\n", message.message);
+    LogPrintLevel(BCLog::IPC, ConvertIPCLogLevel(message.level), "%s\n", message.message);
     if (message.level == mp::Log::Raise) throw Exception(message.message);
 }
 
@@ -64,6 +90,7 @@ class CapnpProtocol : public Protocol
         mp::g_thread_context.thread_name = mp::ThreadName(exe_name);
         mp::LogOptions opts = {
             .log_fn = IpcLogFn,
+            .log_level = GetRequestedIPCLogLevel()
         };
         m_loop.emplace(exe_name, std::move(opts), &m_context);
         if (ready_fn) ready_fn();
@@ -95,6 +122,7 @@ class CapnpProtocol : public Protocol
             util::ThreadRename("capnp-loop");
             mp::LogOptions opts = {
                 .log_fn = IpcLogFn,
+                .log_level = GetRequestedIPCLogLevel()
             };
             m_loop.emplace(exe_name, std::move(opts), &m_context);
             m_loop_ref.emplace(*m_loop);